The present invention relates to a portable terminal wherein program installation is confirmed reliably for preventing a malfunction because of a fall of its power supply.
There is a portable terminal wherein an operating system adequate for an application program is installed optionally, selected from operating systems prepared in a host computer, for example, whereof an example is disclosed in a Japanese patent application laid open as a Provisional Publication No. 241796/'93, entitled "An Install Method of a Terminal System". In the prior art, an easy and reliable method is proposed for installing an operating system in a portable terminal.
FIG. 8 is a schematic diagram illustrating the install method of the prior art for installing programs in a portable terminal 35 connected to a host computer 36 by way of an adapter.
In the portable terminal 35, there are provided a ROM (Read Only Memory) 31, a first RAM (Random Access Memory) 32, and a second RAM 33. In a memory device 34 of the host computer 36, there are prepared an initialization program 341 for initializing the second RAM 33 of the portable terminal 35, a copy program 342, an application program 343, and an application start program 344 including an operating system adequate for the application program 343.
A basic operating system 311, a communication program 312 and an install program 313 are prepared in the ROM 31 of the portable terminal 35.
Now, the installation processes of the portable terminal 35 is described.
When the portable terminal 35 is switched on, the basic operating system 311 and the communication program 312 are activated and the install program 313 is executed. The install program 313 deploys the initialization program 341 in the first RAM 32 by way of the communication program 312 (at step ST1) from the host computer 36. The initialization program 341 initializes the second RAM 33 and deploys the copy program 342 in the first RAM 32 (at step ST2) through the communication program 312. The copy program 342 reads out the application program 343 and the application start program 344 through the communication program 312 and stores them in the second RAM 33 (at step ST3). Then, at the end of the installation processes, the portable terminal 35 is reset and the application start program 344 is activated and deploys the application program 343.
Thus, the application program 343 is execited in the portable terminal 35 on the adequate operating system.
In the portable terminal which is driven by a battery, it is important to prevent malfunction due to a fall of power supply voltage, which may result in the destruction of programs or data stored therein.
FIG. 9 is a block diagram illustrating a portable terminal disclosed in a Japanese patent application entitled "Portable Data Terminal" and laid open as a Provisional Publication No. 86877/'86, wherein the activation of the portable terminal is blocked when a fall of power supply is found or it is connected to a discharged battery.
Referring to FIG. 9, the portable terminal comprises a voltage drop detector 45, a control section 46, a start signal controller 47, a start signal generator 48 and a memory 49. When the power supply voltage drops, it is detected by the voltage drop detector 45 and a voltage drop detection signal is delivered both to the control section 46 and the start signal controller 47.
Receiving the voltage drop detection signal, a protection program in the control section 46 controls the portable terminal to alarm the user and to stop the operation, of the portable terminal if in operation at that time.
When the portable terminal is switched on, the start signal generator 48 delivers a start signal to the start signal controller 47. At the same time, the voltage drop detection signal is also delivered to the start signal controller 47 when the power supply voltage is lower than a certain level. In this case, the start signal is suppressed by the start signal controller 47 and not transmitted to the control section 46. Thus, the portable terminal remains disabled. When the power supply voltage is higher than the certain level, the start signal generated by the start signal generator 48 is transmitted to the control section 46 for activating the portable terminal.
FIGS. 10a and 10b are timing charts illustrating the operation of the start signal controller 47. The voltage drop detection signal 101 becomes HIGH when the power supply voltage is lower than the certain level, and the start signal 102 becomes LOW when indicating to the control section 46 to start program installation. The start signal controller 47 outputs OR logic 103 of the voltage drop detection signal 101 and the start signal 102. So, the signal delivered to the control section 46 remains at HIGH level as shown in FIG. 10a, when the voltage drop is detected, while the same logic with the start signal 102 is transmitted when the voltage drop detection signal 101 is at LOW level as shown in FIG. 10b for indicating to the control section 46 to start the program installation.
Thus, malfunction because of a fall of the power supply voltage is prevented in the prior art for protecting the data or programs stored in the portable terminal.
However, there may be cases where the protection program itself does not work normally because of the fall of the power supply voltage in the portable terminals of the prior art.
In such case, the control section 46 can not control the portable terminal to alarm the user or to disable the portable terminal. So, the portable terminal is left in an abnormal state of operation which consumes the power supply, resulting in a malfunction or a destruction of data or programs stored therein.
There may be also a case where the program installation is started but not accomplished normally. Even when the power supply voltage is confirmed to be higher than the certain level at the time the portable terminal is switched on, a power level in a comparatively small battery provided in the portable terminal may in the installation processes where many parts of the portable terminal begin to operate at once consuming a peak power, resulting in a malfunction of the protection program.
Further, in a portable terminal where operating system and programs are installed from a host computer through a cable or a radio network such as beforehand described, there may be cases that the program installation is not accomplished normally because of a communication error. Therefore, especially when the portable terminal is started without user input, by use of a timer, it may be left not started normally while consuming its battery, resulting in the destruction of data or programs therein.